Electronic regular images (referred to herein as “regular images”) include (or are restricted to) one or more channels that each define values for a human visible spectrum. For example, a visible color image may include a red channel, a blue channel, a green channel, and/or other visible spectrum channel(s). The values defined by each of the channels of a regular image may include a value, for each of a plurality of pixels of the image, that indicates a corresponding frequency and amplitude (intensity) of the pixel in the corresponding spectrum.
Electronic spectral images (referred to herein as “spectral images”) include one or more channels that each define values for a spectrum that is not human visible (and may also optionally include channel(s) that each define values for a human visible spectrum). Some explicit examples of a spectral image are a multispectral image and a hyperspectral image. For example, a spectral image may include a near-infrared channel, a mid-infrared channel, a far-infrared channel, a thermal-infrared channel, an ionizing radiation channel, a micro-wave channel, a radio wave channel, an ultra-low frequency channel, a super low frequency channel, and/or other channels that are not human visible. Also, a spectral image may include one or more channels that are each subsets of one of the aforementioned channels (or other channels). For example, multiple micro-wave channels, each covering a different range of frequencies, may be provided in lieu of a single micro-wave channel. The values defined by each of the channels of a spectral image may include a value, for each of a plurality of pixels of the image, that indicates a corresponding frequency of the pixel in the corresponding spectrum.